Re: Problems Upgrading firmware on nanoNNA H4.
STM32 Bootloader *IS* correct - Dfuse should be able to see that if it's drivernhas been correctly installed. (Comes with Dfuse, not Whinders . . .)
toggle quoted message
Show quoted text
On March 8, 2024 1:41:54 PM EST, David Grace <davidGW4OUU@...> wrote: Thanks for the responses but DfuSeDemo doesnt recognise the vna either.
When connected normally it appears in Device Manager under ports as a vitual com port . When in dfu mode that disappears and reappears as a usb device ,STM32 BOOTLOADER.
However the nanovna app doesnt see that !!
________________________________
From: [email protected] <[email protected]> on behalf of Siegfried Jackstien <siegfried.jackstien@...>
Sent: 08 March 2024 17:08
To: [email protected] <[email protected]>
Subject: Re: [nanovna-users] Problems Upgrading firmware on nanoNNA H4.
and..if you use nanovna app.. and change device to update mode.. com port number may change...
select that comport... click on connect in app and the soft will say "found vna in upload mode.. do you want to upgrade fw?"
easy as baking cakes
dg9bfc sigi
Am 08.03.2024 17:48 schrieb Tim Dawson <tadawson@...>:
If you have DfuSeDemo installed, what is preventing you from doing the
upgrade with it?
Oh, and when in Dfu mode, the Nano's ID changes, so you would see it as a
Dfu device, not as the NanoVNA - that much is normal.
On March 8, 2024 11:41:17 AM EST, David Grace <davidGW4OUU@...>
wrote:
I have been unable to carry out this update. I currently have vesion 0.5.0.
I have downloaded several newer versions, have DfuSedemo installed with up to date drivers - did i say i am using windows 10.
I have aslo got NanoVNA-APP installed. this recognises the vna and will download screens from it which indicates that the lead i am using is ok,
but when i put the vna into dfu mode it no longer recognises the vna.
I have tried all this in 'administrator' mode without any luck !
Help - what am i doing wrong ?
--
Sent from my Android device with K-9 Mail. Please excuse my brevity.
--
Sent from my Android device with K-9 Mail. Please excuse my brevity.
|
Re: Problems Upgrading firmware on nanoNNA H4.
Thanks for the responses but DfuSeDemo doesnt recognise the vna either. When connected normally it appears in Device Manager under ports as a vitual com port . When in dfu mode that disappears and reappears as a usb device ,STM32 BOOTLOADER. However the nanovna app doesnt see that !! ________________________________ From: [email protected] < [email protected]> on behalf of Siegfried Jackstien <siegfried.jackstien@...> Sent: 08 March 2024 17:08 To: [email protected] < [email protected]> Subject: Re: [nanovna-users] Problems Upgrading firmware on nanoNNA H4. and..if you use nanovna app.. and change device to update mode.. com port number may change... select that comport... click on connect in app and the soft will say "found vna in upload mode.. do you want to upgrade fw?" easy as baking cakes dg9bfc sigi Am 08.03.2024 17:48 schrieb Tim Dawson <tadawson@...>:
If you have DfuSeDemo installed, what is preventing you from doing the
upgrade with it?
Oh, and when in Dfu mode, the Nano's ID changes, so you would see it as a
Dfu device, not as the NanoVNA - that much is normal.
On March 8, 2024 11:41:17 AM EST, David Grace <davidGW4OUU@...>
wrote:
I have been unable to carry out this update. I currently have vesion 0.5.0.
I have downloaded several newer versions, have DfuSedemo installed with up to date drivers - did i say i am using windows 10.
I have aslo got NanoVNA-APP installed. this recognises the vna and will download screens from it which indicates that the lead i am using is ok,
but when i put the vna into dfu mode it no longer recognises the vna.
I have tried all this in 'administrator' mode without any luck !
Help - what am i doing wrong ?
--
Sent from my Android device with K-9 Mail. Please excuse my brevity.
|
Re: Problems Upgrading firmware on nanoNNA H4.
and..if you use nanovna app.. and change device to update mode.. com port number may change...
select that comport... click on connect in app and the soft will say "found vna in upload mode.. do you want to upgrade fw?"
easy as baking cakes
dg9bfc sigi
Am 08.03.2024 17:48 schrieb Tim Dawson <tadawson@...>:
toggle quoted message
Show quoted text
If you have DfuSeDemo installed, what is preventing you from doing the
upgrade with it?
Oh, and when in Dfu mode, the Nano's ID changes, so you would see it as a
Dfu device, not as the NanoVNA - that much is normal.
On March 8, 2024 11:41:17 AM EST, David Grace <davidGW4OUU@...>
wrote:
I have been unable to carry out this update.? I currently have vesion 0.5.0.
I have downloaded several newer versions, have? DfuSedemo installed with up to date drivers - did i say i am using windows 10.
I have aslo got NanoVNA-APP installed. this recognises the vna and will download screens from it which indicates that the lead i am using is ok,
but when i put the vna into dfu mode it no longer recognises the vna.
I have tried all this in 'administrator' mode without any luck !
Help - what am i doing wrong ?
--
Sent from my Android device with K-9 Mail. Please excuse my brevity.
|
Re: Problems Upgrading firmware on nanoNNA H4.
If you have DfuSeDemo installed, what is preventing you from doing the upgrade with it?
Oh, and when in Dfu mode, the Nano's ID changes, so you would see it as a Dfu device, not as the NanoVNA - that much is normal.
toggle quoted message
Show quoted text
On March 8, 2024 11:41:17 AM EST, David Grace <davidGW4OUU@...> wrote: I have been unable to carry out this update. I currently have vesion 0.5.0.
I have downloaded several newer versions, have DfuSedemo installed with up to date drivers - did i say i am using windows 10.
I have aslo got NanoVNA-APP installed. this recognises the vna and will download screens from it which indicates that the lead i am using is ok, but when i put the vna into dfu mode it no longer recognises the vna.
I have tried all this in 'administrator' mode without any luck !
Help - what am i doing wrong ?
--
Sent from my Android device with K-9 Mail. Please excuse my brevity.
|
Problems Upgrading firmware on nanoNNA H4.
I have been unable to carry out this update. I currently have vesion 0.5.0.
I have downloaded several newer versions, have DfuSedemo installed with up to date drivers - did i say i am using windows 10.
I have aslo got NanoVNA-APP installed. this recognises the vna and will download screens from it which indicates that the lead i am using is ok, but when i put the vna into dfu mode it no longer recognises the vna.
I have tried all this in 'administrator' mode without any luck !
Help - what am i doing wrong ?
|
Note that if you do the SOL calibration not with a load of 50 ¦¸ but with, for example, a load of 75 ¦¸, then the values displayed from the S11 are correct (compared to 75 ¦¸) and the same for the .s1p file For the values calculated by the box (R for example), you must make a rule of 3 but if you recalculate from the .s1p file taking into account the "normalization" to 75 ¦¸, the values will be correct.
--
F1AMM
Fran?ois
|
On Thu, Mar 7, 2024 at 10:52 AM, Brian Beezley wrote:
Maybe others can comment on their experience with various noncoaxial VNA
loads.
I have found that the impedance/match of chip resistors depends upon how it is mounted, positioning the resistive element towards or away from the ground plane, or on edge, changes its shunt capacitance and can make a big difference in tis performance. Then of course there is the way it is grounded..... I have settled on using 3, 150¦¸ resistors arrayed radially when building a termination onto a coaxial connector. 73, Don N2VGU
|
Re: DFU drivers not loading
Are you looking for DFU mode to update the firmware? If so, you might consider the VNA App program. It is similar to the VNA saver application, but it has a built in firmware upload function.
|
I suspect that there's so many applications where a 50 ohm resistor is nice (e.g. driving coax from a low Z source, as a series termination), or as a RF termination with a High Z receiver.
yeah, it's not a standard value in the sequence, but there clearly is a demand.
Last time I was buying non-inductive resistors for HF dummy loads from Caddock, they had 50 ohms.
The 49.9 is really an artifact of the standard sequence with the same ratio between successive values. The 1., 1.2, 1.5, 2.2, 3.3 etc.
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-----Original Message----- From: < [email protected]> Sent: Mar 7, 2024 7:52 AM To: < [email protected]> Subject: [nanovna-users] VNA Calibration Load When considering a VNA calibration load for various projects, I used to specify two 100-ohm 1% resistors in parallel, which halves stray inductance. Of course it also doubles stray capacitance, which may be a worse problem. So I started specifying a single 49.9-ohm 1% resistor. I was surprised to discover that 50-ohm 1% resistors are available. I was really surprised when I noticed the price for 0.1% parts: ;termination%20style=Axial~~SMD%2FSMT&tolerance=0.1%20%25&instock=y&sort=pricing&rp=passive-components%2Fresistors%7C~Termination%20Style It's unlikely a NanoVNA application needs 0.1% accuracy, but the parts are so cheap, why not? If you look at the Vishay datasheet for the first part, you'll see graphs for resistance magnitude and phase angle for several part sizes, most to 3 GHz. The curves look pretty good. I've never actually used these parts, but they look good on paper. Maybe others can comment on their experience with various noncoaxial VNA loads. Brian
|
One advantage of using cal loads that are very close to 50 ohms resistance is that you get better estimates when measuring high and low impedances using the S11 shunt method. I use home built calibration load that isconstructed with a precision 50 ohm 0805 SMD resistor . Used a nanoVNA-H4 to measure 1 ohm and 3000 ohm 0805 SMD components and got what I consider excellent results.
Roger
|
That's a great reference, Dragan. Thanks for posting it. It's interesting that IN3OTD found the 0805 pair to perform best. In the Vishay curves, the smaller sizes look considerably better. The Vishay 0805 curve even stops at 500 MHz while the smaller resistors go to 3 GHz. I wonder if the IN3OTD/Vishay discrepancy is due to different resistor manufacturers or to details of the test setup. Vishay curve note: Typical figures, HF-characteristic also depends on termination and circuit design.
Brian
|
On Thu, 7 Mar 2024 at 18:23, Reinier Gerritsen <reinier123@...> wrote:
I have seen measurements of homemade calibration loads. optimum was 2
resistors of 100 Ohm in parallel. It performed better than a single 49R9
resistor or 3 x 150 Ohm resistors.
Some interesting links:
Couldn't find the link evaluating different load styles.
Op 7-3-2024 om 16:52 schreef Brian Beezley:
When considering a VNA calibration load for various projects, I used to specify two 100-ohm 1% resistors in parallel, which halves stray inductance. Of course it also doubles stray capacitance, which may be a worse problem. So I started specifying a single 49.9-ohm 1% resistor. I was surprised to discover that 50-ohm 1% resistors are available. I was really surprised when I noticed the price for 0.1% parts:
It's unlikely a NanoVNA application needs 0.1% accuracy, but the parts are so cheap, why not? If you look at the Vishay datasheet for the first part,
you'll see graphs for resistance magnitude and phase angle for several part sizes, most to 3 GHz. The curves look pretty good.
I've never actually used these parts, but they look good on paper. Maybe others can comment on their experience with various noncoaxial VNA loads.
Brian
|
I have seen measurements of homemade calibration loads. optimum was 2 resistors of 100 Ohm in parallel. It performed better than a single 49R9 resistor or 3 x 150 Ohm resistors.
Some interesting links:
Couldn't find the link evaluating different load styles.
Op 7-3-2024 om 16:52 schreef Brian Beezley:
toggle quoted message
Show quoted text
When considering a VNA calibration load for various projects, I used to specify two 100-ohm 1% resistors in parallel, which halves stray inductance. Of course it also doubles stray capacitance, which may be a worse problem. So I started specifying a single 49.9-ohm 1% resistor. I was surprised to discover that 50-ohm 1% resistors are available. I was really surprised when I noticed the price for 0.1% parts:
It's unlikely a NanoVNA application needs 0.1% accuracy, but the parts are so cheap, why not? If you look at the Vishay datasheet for the first part,
you'll see graphs for resistance magnitude and phase angle for several part sizes, most to 3 GHz. The curves look pretty good.
I've never actually used these parts, but they look good on paper. Maybe others can comment on their experience with various noncoaxial VNA loads.
Brian
|
When considering a VNA calibration load for various projects, I used to specify two 100-ohm 1% resistors in parallel, which halves stray inductance. Of course it also doubles stray capacitance, which may be a worse problem. So I started specifying a single 49.9-ohm 1% resistor. I was surprised to discover that 50-ohm 1% resistors are available. I was really surprised when I noticed the price for 0.1% parts:
It's unlikely a NanoVNA application needs 0.1% accuracy, but the parts are so cheap, why not? If you look at the Vishay datasheet for the first part,
you'll see graphs for resistance magnitude and phase angle for several part sizes, most to 3 GHz. The curves look pretty good.
I've never actually used these parts, but they look good on paper. Maybe others can comment on their experience with various noncoaxial VNA loads.
Brian
|
Re: Question on remote use of NanoVNA
Jim,
That's a good point. I also ran across USB stick Wifi routers, I have to dig into what could be expected there.
I did some browsing last night and found some information that although android phones have the hardware capability to use an adhoc connection - its disabled in the software.
You would have to root the device and further develop it. But using the phone as the host and assigning a static IP as you've mentioned still seems viable and perhaps the simplest.
Andy
|
Re: where is the end fed natural resonance
It was a busy time. Papers galore.
In electrical engineering ( ) and telecommunications ( ) the *Chu¨CHarrington limit* or *Chu limit* sets a lower limit on the Q factor ( ) for a small radio antenna ( ). [1] ( ) The theorem was developed in several papers between 1948 and 1960 by Lan Jen Chu ( ) , [2] ( ) Harold Wheeler ( ) , [3] ( ) and later by Roger F. Harrington ( ). [4] ( ) The definition of a small antenna is one that can fit inside a sphere whose diameter is
(radius
) ¨C a little smaller than 1 ? 3 wavelength ( ) in its widest dimension. For a small antenna the Q is proportional to the reciprocal of the volume of a sphere ( ) that encloses it. In practice this means that there is a limit to the bandwidth of data that can be sent to and received from small antennas such as are used in mobile phones ( ).
More specifically, Chu established the limit on Q for a lossless antenna as
for a linear polarized ( ) antenna, where
is the radius of the smallest sphere containing the antenna and its current distribution and
is the wavenumber ( ). A circular polarized antenna can be half the size [5] ( ) (an extension of the theory of Chu by Harrington). [6] ( )
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On Mar 4, 2024, at 8:26?PM, Jim Lux <jimlux@...> wrote:
? Harrington & Chu, but yes.
On Mar 4, 2024, at 7:52?PM, AG6CX <edwmccann@...> wrote:
?Didn¡¯t Chu - Wheeler nail this one?
Ed McCann
AG6CX
MSEE MIT
On Mar 4, 2024, at 7:47?PM, W0LEV <davearea51a@...> wrote:
?One of the exercises we had in grad school was to prove that a radiating
structure could be down-sized to 10% of its full and ideal size without
losing efficiency, all other parameters being equal. ?The devil is in the
details, "all other parameters being equal".
Dave - W?LEV
On Tue, Mar 5, 2024 at 2:46?AM Jim Lux <jimlux@...> wrote:
How you define efficiency? ?If there¡¯s no loss, then an infinitely small
antenna (a hertzian dipole, for instance) just has 1.5 dB gain over an
isotropic antenna. Small antennas have low radiation resistance, but that
only affects efficiency if there¡¯s loss.
For the run of the mill, nearly full sized, dipole, whether or not it¡¯s
resonant doesn¡¯t change the radiation resistance much, neither does it
change the loss resistance, so the efficiency doesn¡¯t change much.
What might change is the loss in the matching network or feedline.
The compact loop is notorious for having high loss because it has low
radiation resistance compared to loss resistance. ?As is a mobile whip on
40 meters and down - they¡¯re a tiny fraction of a wavelength, so the
radiation resistance is low.
On Mar 4, 2024, at 1:01?PM, W0LEV <davearea51a@...> wrote:
?QUOTE (Jim Lux): ?.....short antennas have a different pattern than full
size antenna, but their "efficiency" isn't intrinsically different).
Jim, if we address small tuned loops on transmit, the efficiency over a
dipole radiator is considerably less, in round numbers, -20 dB.
In the limit of a point radiator (if it could radiate) - a true isotropic
source, the efficiency is zip, zero.
Dave - W?LEV
On Mon, Mar 4, 2024 at 7:28?PM Jim Lux <jimlux@...> wrote:
This is using resonance as a choke, not resonance of the entire antenna.
You want your choke to be high Z, so that currents don't flow on the
outside of the coax.
As far as the antenna goes, if you can drive it or couple power to/from
it, whether it's resonant or not makes no difference on the performance.
(aside from any other length related issues - short antennas have a
different pattern than full size antenna, but their "efficiency" isn't
intrinsically different).
-----Original Message-----
From: <[email protected]>
Sent: Mar 4, 2024 9:54 AM
To: <[email protected]>
Subject: Re: [nanovna-users] where is the end fed natural resonance
But then ARRL Antenna book says resonance has no affect on antenna
performance. Hams like to operate antennas at or near resonance as
that’s where drive point impedance is at its lowest value so
it’s easier to match,
Ray
--
*Dave - W?LEV*
--
Dave - W?LEV
--
*Dave - W?LEV*
--
Dave - W?LEV
|
Re: where is the end fed natural resonance
*
Understanding the bandwidth limitations of small antennas: Wheeler, Chu and today
*
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*Abstract:* Wheeler's 1947 paper presented the first detailed discussion on the limitations on antenna Q-factor vs. size. In light of recent work on the lower bounds on Q for antenna... View more
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Contents
I. Introduction
---------------
In 1947, Harold Wheeler published the following formula for the radiation -factor of an electrically small cylindrical dipole antenna [1]:
Q = 6 ¦Ð ¦Ê V k 3 (1)
where is the volume of the antenna, is the wavenumber, and is defined as the ¡®shape factor¡¯. The shape factor is defined by Wheeler as the correction factor required to determine the capacitance or inductance of the structure from its geometry (e.g. in the case of the capacitor, multiplies the cross-sectional area to account for the effects of the fringing fields outside the cylindrical volume).
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Show quoted text
On Mar 4, 2024, at 8:26?PM, Jim Lux <jimlux@...> wrote:
? Harrington & Chu, but yes.
On Mar 4, 2024, at 7:52?PM, AG6CX <edwmccann@...> wrote:
?Didn¡¯t Chu - Wheeler nail this one?
Ed McCann
AG6CX
MSEE MIT
On Mar 4, 2024, at 7:47?PM, W0LEV <davearea51a@...> wrote:
?One of the exercises we had in grad school was to prove that a radiating
structure could be down-sized to 10% of its full and ideal size without
losing efficiency, all other parameters being equal. ?The devil is in the
details, "all other parameters being equal".
Dave - W?LEV
On Tue, Mar 5, 2024 at 2:46?AM Jim Lux <jimlux@...> wrote:
How you define efficiency? ?If there¡¯s no loss, then an infinitely small
antenna (a hertzian dipole, for instance) just has 1.5 dB gain over an
isotropic antenna. Small antennas have low radiation resistance, but that
only affects efficiency if there¡¯s loss.
For the run of the mill, nearly full sized, dipole, whether or not it¡¯s
resonant doesn¡¯t change the radiation resistance much, neither does it
change the loss resistance, so the efficiency doesn¡¯t change much.
What might change is the loss in the matching network or feedline.
The compact loop is notorious for having high loss because it has low
radiation resistance compared to loss resistance. ?As is a mobile whip on
40 meters and down - they¡¯re a tiny fraction of a wavelength, so the
radiation resistance is low.
On Mar 4, 2024, at 1:01?PM, W0LEV <davearea51a@...> wrote:
?QUOTE (Jim Lux): ?.....short antennas have a different pattern than full
size antenna, but their "efficiency" isn't intrinsically different).
Jim, if we address small tuned loops on transmit, the efficiency over a
dipole radiator is considerably less, in round numbers, -20 dB.
In the limit of a point radiator (if it could radiate) - a true isotropic
source, the efficiency is zip, zero.
Dave - W?LEV
On Mon, Mar 4, 2024 at 7:28?PM Jim Lux <jimlux@...> wrote:
This is using resonance as a choke, not resonance of the entire antenna.
You want your choke to be high Z, so that currents don't flow on the
outside of the coax.
As far as the antenna goes, if you can drive it or couple power to/from
it, whether it's resonant or not makes no difference on the performance.
(aside from any other length related issues - short antennas have a
different pattern than full size antenna, but their "efficiency" isn't
intrinsically different).
-----Original Message-----
From: <[email protected]>
Sent: Mar 4, 2024 9:54 AM
To: <[email protected]>
Subject: Re: [nanovna-users] where is the end fed natural resonance
But then ARRL Antenna book says resonance has no affect on antenna
performance. Hams like to operate antennas at or near resonance as
that’s where drive point impedance is at its lowest value so
it’s easier to match,
Ray
--
*Dave - W?LEV*
--
Dave - W?LEV
--
*Dave - W?LEV*
--
Dave - W?LEV
|
Re: where is the end fed natural resonance
Harrington & Chu, but yes.
toggle quoted message
Show quoted text
On Mar 4, 2024, at 7:52?PM, AG6CX <edwmccann@...> wrote:
?Didn¡¯t Chu - Wheeler nail this one?
Ed McCann
AG6CX
MSEE MIT
On Mar 4, 2024, at 7:47?PM, W0LEV <davearea51a@...> wrote:
?One of the exercises we had in grad school was to prove that a radiating
structure could be down-sized to 10% of its full and ideal size without
losing efficiency, all other parameters being equal. The devil is in the
details, "all other parameters being equal".
Dave - W?LEV
On Tue, Mar 5, 2024 at 2:46?AM Jim Lux <jimlux@...> wrote: How you define efficiency? If there¡¯s no loss, then an infinitely small
antenna (a hertzian dipole, for instance) just has 1.5 dB gain over an
isotropic antenna. Small antennas have low radiation resistance, but that
only affects efficiency if there¡¯s loss.
For the run of the mill, nearly full sized, dipole, whether or not it¡¯s
resonant doesn¡¯t change the radiation resistance much, neither does it
change the loss resistance, so the efficiency doesn¡¯t change much.
What might change is the loss in the matching network or feedline.
The compact loop is notorious for having high loss because it has low
radiation resistance compared to loss resistance. As is a mobile whip on
40 meters and down - they¡¯re a tiny fraction of a wavelength, so the
radiation resistance is low.
On Mar 4, 2024, at 1:01?PM, W0LEV <davearea51a@...> wrote: ?QUOTE (Jim Lux): .....short antennas have a different pattern than full
size antenna, but their "efficiency" isn't intrinsically different).
Jim, if we address small tuned loops on transmit, the efficiency over a
dipole radiator is considerably less, in round numbers, -20 dB.
In the limit of a point radiator (if it could radiate) - a true isotropic
source, the efficiency is zip, zero.
Dave - W?LEV
On Mon, Mar 4, 2024 at 7:28?PM Jim Lux <jimlux@...> wrote:
This is using resonance as a choke, not resonance of the entire antenna.
You want your choke to be high Z, so that currents don't flow on the
outside of the coax.
As far as the antenna goes, if you can drive it or couple power to/from
it, whether it's resonant or not makes no difference on the performance.
(aside from any other length related issues - short antennas have a
different pattern than full size antenna, but their "efficiency" isn't
intrinsically different).
-----Original Message-----
From: <[email protected]>
Sent: Mar 4, 2024 9:54 AM
To: <[email protected]>
Subject: Re: [nanovna-users] where is the end fed natural resonance
But then ARRL Antenna book says resonance has no affect on antenna
performance. Hams like to operate antennas at or near resonance as
that’s where drive point impedance is at its lowest value so
it’s easier to match,
Ray
--
*Dave - W?LEV*
--
Dave - W?LEV
--
*Dave - W?LEV*
--
Dave - W?LEV
|
Re: where is the end fed natural resonance
Didn¡¯t Chu - Wheeler nail this one?
Ed McCann
AG6CX
MSEE MIT
toggle quoted message
Show quoted text
On Mar 4, 2024, at 7:47?PM, W0LEV <davearea51a@...> wrote:
?One of the exercises we had in grad school was to prove that a radiating
structure could be down-sized to 10% of its full and ideal size without
losing efficiency, all other parameters being equal. The devil is in the
details, "all other parameters being equal".
Dave - W?LEV
On Tue, Mar 5, 2024 at 2:46?AM Jim Lux <jimlux@...> wrote:
How you define efficiency? If there¡¯s no loss, then an infinitely small
antenna (a hertzian dipole, for instance) just has 1.5 dB gain over an
isotropic antenna. Small antennas have low radiation resistance, but that
only affects efficiency if there¡¯s loss.
For the run of the mill, nearly full sized, dipole, whether or not it¡¯s
resonant doesn¡¯t change the radiation resistance much, neither does it
change the loss resistance, so the efficiency doesn¡¯t change much.
What might change is the loss in the matching network or feedline.
The compact loop is notorious for having high loss because it has low
radiation resistance compared to loss resistance. As is a mobile whip on
40 meters and down - they¡¯re a tiny fraction of a wavelength, so the
radiation resistance is low.
On Mar 4, 2024, at 1:01?PM, W0LEV <davearea51a@...> wrote: ?QUOTE (Jim Lux): .....short antennas have a different pattern than full
size antenna, but their "efficiency" isn't intrinsically different).
Jim, if we address small tuned loops on transmit, the efficiency over a
dipole radiator is considerably less, in round numbers, -20 dB.
In the limit of a point radiator (if it could radiate) - a true isotropic
source, the efficiency is zip, zero.
Dave - W?LEV
On Mon, Mar 4, 2024 at 7:28?PM Jim Lux <jimlux@...> wrote:
This is using resonance as a choke, not resonance of the entire antenna.
You want your choke to be high Z, so that currents don't flow on the
outside of the coax.
As far as the antenna goes, if you can drive it or couple power to/from
it, whether it's resonant or not makes no difference on the performance.
(aside from any other length related issues - short antennas have a
different pattern than full size antenna, but their "efficiency" isn't
intrinsically different).
-----Original Message-----
From: <[email protected]>
Sent: Mar 4, 2024 9:54 AM
To: <[email protected]>
Subject: Re: [nanovna-users] where is the end fed natural resonance
But then ARRL Antenna book says resonance has no affect on antenna
performance. Hams like to operate antennas at or near resonance as
that’s where drive point impedance is at its lowest value so
it’s easier to match,
Ray
--
*Dave - W?LEV*
--
Dave - W?LEV
--
*Dave - W?LEV*
--
Dave - W?LEV
|
Re: where is the end fed natural resonance
One of the exercises we had in grad school was to prove that a radiating
structure could be down-sized to 10% of its full and ideal size without
losing efficiency, all other parameters being equal. The devil is in the
details, "all other parameters being equal".
Dave - W?LEV
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On Tue, Mar 5, 2024 at 2:46?AM Jim Lux <jimlux@...> wrote: How you define efficiency? If there¡¯s no loss, then an infinitely small
antenna (a hertzian dipole, for instance) just has 1.5 dB gain over an
isotropic antenna. Small antennas have low radiation resistance, but that
only affects efficiency if there¡¯s loss.
For the run of the mill, nearly full sized, dipole, whether or not it¡¯s
resonant doesn¡¯t change the radiation resistance much, neither does it
change the loss resistance, so the efficiency doesn¡¯t change much.
What might change is the loss in the matching network or feedline.
The compact loop is notorious for having high loss because it has low
radiation resistance compared to loss resistance. As is a mobile whip on
40 meters and down - they¡¯re a tiny fraction of a wavelength, so the
radiation resistance is low.
On Mar 4, 2024, at 1:01?PM, W0LEV <davearea51a@...> wrote:
?QUOTE (Jim Lux): .....short antennas have a different pattern than full
size antenna, but their "efficiency" isn't intrinsically different).
Jim, if we address small tuned loops on transmit, the efficiency over a
dipole radiator is considerably less, in round numbers, -20 dB.
In the limit of a point radiator (if it could radiate) - a true isotropic
source, the efficiency is zip, zero.
Dave - W?LEV
On Mon, Mar 4, 2024 at 7:28?PM Jim Lux <jimlux@...> wrote:
This is using resonance as a choke, not resonance of the entire antenna.
You want your choke to be high Z, so that currents don't flow on the
outside of the coax.
As far as the antenna goes, if you can drive it or couple power to/from
it, whether it's resonant or not makes no difference on the performance.
(aside from any other length related issues - short antennas have a
different pattern than full size antenna, but their "efficiency" isn't
intrinsically different).
-----Original Message-----
From: <[email protected]>
Sent: Mar 4, 2024 9:54 AM
To: <[email protected]>
Subject: Re: [nanovna-users] where is the end fed natural resonance
But then ARRL Antenna book says resonance has no affect on antenna
performance. Hams like to operate antennas at or near resonance as
that’s where drive point impedance is at its lowest value so
it’s easier to match,
Ray
--
*Dave - W?LEV*
--
Dave - W?LEV
-- *Dave - W?LEV*
--
Dave - W?LEV
|
Donald S Brant Jr
Roger Need
